Midland Radio SP-300 service manual VCO Lock Time

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MAXON

SP-300 Series HAND HELD

VCO Lock Time

The micro will allow more lock time for the VCO before the out-of-lock beep indication.

Low Battery Indication

Low Battery Indication will be changed so that it does not inhibit RX and will allow one transmission after low cell is indicated. Low cell will not be indicated during transmit mode. If the battery goes below specified limits during the TX mode, low cell will be indicated immediately after releasing the PTT button.

After the low cell indication is issued, the transmitter can only be used one time. When the PTT is pushed again and then released, the transmitter is locked out until the unit is powered down and then powered back up.

Memory Protect

The software is such that if the radio is inadvertently put into program mode it will not lose the contents of the EEPROM memory. Data will only move in and out of the memory when the programmer is attached.

External Option Detect

An input to the microprocessor will be available that will indicate to the microprocessor that the external option has been selected. This input should be connected to the exter- nal option connector. External option should be selected for each channel. If a channel is selected during programming for external option, this input should be active when the channel is selected during operation of the unit.

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May 2001

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Contents Service Manual Table of Contents Board Layout Exploded View General SpecificationsTemperature Range Current ConsumptionAdjacent Channel Power DimensionsWeight Frequency BandsReceiver Peak Deviation @ 1 kHz Nom. Dev +20dBRX Tone Demodulation Characteristics Features SP-300INTRODUCTIONBusy Channel Lockout VCO Lock Time Description of Controls DescriptionTheory of Operation Digital CircuitsRF Circuits RF Circuits PLL Synthesizer Noise Detector Squelch mute CircuitKHz Band Pass Filter Speaker Audio AmplifierRemoving the belt clip Maintenance and RepairRemoving & Replacing the Belt Clip To replace the belt clipTo replace the battery Removing & Replacing the BatteryTo remove the battery To remove the PTT assemblyRemoving & Replacing the ACCES- Sory Connector Removing & Replacing the Antenna & Control KnobsTo remove the Back Cover Removing & Replacing the Back CoverTo replace the Back Cover Removing & Replacing the Main Board To remove the Main BoardTo replace the Main Board Removing & Replacing the DAUGH- TER Boards Component ReplacementRemoving & Replacing the Speaker Surface Mount Component Replacement Surface Mounted Integrated Circuit ReplacementProgramming Alignment ProcedureCloning RX VCO Test Equipment Setup S.G. @ 1kHz AudioAlignment Points Diagram TP1Troubleshooting Guide Symptoms Causes Counter MeasuresVoltage Charts Main CircuitReceive State Transmit State SP-300 Series UHF & VHF Digital Section Parts List REF# Description PART#-30- May SP-300 Series VHF RF Section Parts List REF # Description Replacement Modules-32- May -33- May SP-300 Series UHF RF Section Parts List -35- May -36- May -37- May Component Pinout KTA1504SY-39- May Base Diagram PIN Description VHF FRONT-END VHF Power AMPUHF Power AMP UHF FRONT-ENDVHF V.C.O UHF V.C.OTcxo ACC-200 BatteryFuse SP-300 Series VHF RF Schematic UHF RF Schematic -47- May Board Layout Top Main Board Assembly 416121B -49- May